Fix broken cross-package Haddock links on hosted docs site

Fixes #601. Cross-package hrefs emitted by cabal haddock-project are
relative paths (e.g. href="../cardano-ledger-api-1.2.3-hash/Foo.html")
that don't resolve on the published site — we only host cardano-api's
own output, not its dependencies, so every cross-package reference
404s by default.

Add scripts/fix-haddock-links.sh and wire it into the github-page
workflow between haddock-project and the artifact upload. The script
replaces each cross-package href with one of:

  * an absolute URL on the upstream doc site, when the package is on
    CHaP and we find a valid hosted module page for it;
  * a tooltip-annotated, unclickable <span>, when the package is not
    on CHaP (bootlibs like base, bytestring, time are deliberately
    not linked — Haddock's URL shapes don't match Hackage's well and
    readers rarely follow the links anyway), or is on CHaP but has
    no known doc site, or the upstream module page itself 404s.

The published site thus has zero clickable 404s.

Doc-site resolution
  For each CHaP package, two lookups in order, first hit wins:
    1. Name-suffix heuristic under *.cardano.intersectmbo.org: drop
       trailing "-token" segments of the package name, HEAD-probe
       each candidate's doc-index.html. Covers cardano-ledger-*,
       plutus-*, ouroboros-*, etc.
    2. Fixed fallback against IOG_DOC_BASES: a six-entry list of
       known IOG doc-site roots for families whose subdomain isn't a
       name-suffix (cardano-base at base.cardano…, network-mux at
       ouroboros-network.cardano…, io-classes at io-sim, etc.).
  Misses become "Unmapped CHaP" and fall into the CI policy below.

Post-rewrite: Phase 2b uses Haddock's emitted "Source" cabal-store
links as ground truth to rewrite local re-export pages back to the
defining upstream package (e.g. references to cardano-ledger-byron's
Address via Cardano.Api.Byron). Phase 3 HEAD-validates each rewritten
URL and rescues dead ones by probing subdirectories (api/, protocols/,
framework/) and parent-module fallbacks with #t: fragment
reconstruction.

Dead-link CI policy (two buckets)
  Actionable (FAILS CI) — CHaP packages the probe couldn't resolve.
    Usually a gap in IOG_DOC_BASES; fix by adding the doc site or
    adding the package to KNOWN_UNDOCUMENTED if genuinely unpublished.
  Unfixable (logs only, does NOT fail CI) — three sub-causes, all
    outside this repo:
      a. Module-level 404s on valid upstream sites; empirically
         upstream publishes only umbrella modules (Cardano-Binary.html)
         while Haddock generates hrefs to the defining sub-module
         (Cardano-Binary-FromCBOR.html).
      b. Packages in KNOWN_UNDOCUMENTED (no published Haddocks
         anywhere — currently kes-agent and kes-agent-crypto).
      c. Haddock-emitted versionless Hackage URLs that Hackage's
         routing doesn't accept.
  GitHub Actions actionable entries emit ::warning:: annotations;
  unfixable ones are plain log lines so they don't flood the UI.
  Env escape FIX_HADDOCK_LINKS_ALLOW_DEAD=1 forces exit 0 anyway.

Author: Jimbo4350

.github/workflows/github-page.yml

@@ -39,6 +39,10 @@ jobs:
           mkdir website
           cabal haddock-project --output=./website --internal --foreign-libraries
 
+      - name: Fix cross-package Haddock links
+        run: |
+          ./scripts/fix-haddock-links.sh ./website
+
       - name: Build typedoc documentation
         run: |
           nix build .#wasm-typedoc